Lithium anode assembly for an electrochemical cell

ABSTRACT

In electrochemical cells for medical devices having anodes assemblies, an anode assembly includes a folded lithium element having a first and second section. The first and second sections are for receiving a current collector therebetween. A method of forming an anode arrangement includes a step of folding a lithium element having the first and second sections with a current collector positioned therebetween. Thereafter, a pressing step is performed.

This application is a continuation of application Ser. No. 08/882,616filed Jun. 25, 1997.

FIELD OF THE INVENTION

The present invention relates to a foldable lithium element and anodeassemblies in an electrochemical cell for use with medical devices. Thisinvention further relates to methods of making such anode assemblies.

BACKGROUND OF THE INVENTION

Electrochemical cells having thin planar anode assemblies have foundparticular applications in the medical field for use with heartpacemakers and other medical devices. General teachings concerning suchcells may be found, for example, in U.S. Pat. No. 5,209,994 (hereinafter'994), assigned to the assignee of the present invention. The '994 cellincludes a container of electrically conductive material which serves asa cathode current collector. The anode assembly of the cell includes alithium element formed from two lithium halves which are pressedtogether with an anode current collector therebetween. The anode currentcollector extends to the exterior of the cell with use of an insulatorwhich insulates a lead connected thereto from electrical contact withthe container. The container is filled with a cathode material which isin operative contact with the exposed surfaces of the lithium element ofthe anode assembly. Similarly, the cathode material is in operativecontact with the container. For enhanced performance of the cell, theopposed, major lateral surfaces (i.e., the “operative surfaces”) of thelithium element may be coated with a film of electron donor material.More specifically, '994 describes this donor material as being apolymeric organic donor material such as poly (2-vinylpyridine). Suchdonor materials and application techniques for such materials are morefully described in U.S. Pat. No. 4,182,798.

In operation, a chemical reaction between the lithium element and thecathode material in the container causes excess electrons to flow intothe current collector. A chemical reaction between the cathode materialand the container causes the container to be positively charged. Theresulting voltage differential can be used to power a device. To preventthe cell from short-circuiting, the anode current collector iselectrically insulated from the cathodic container and from the cathodematerial which fills the container. As noted above, an insulator (i.e.,a feedthrough) allows the anode current collector to extend to theexterior of the container without making electrical contact with thecathodic container. Additionally, the anode current collector isprotected from contact with the cathode material by the seal formed bycohesion between the two lithium halves between which the collector isembedded.

In a conventional method for forming an anode assembly, two lithiumpre-cut elements are positioned on opposite sides of an anode currentcollector. An insulated portion of the anode current collector whichinsulates the collector from the cathodic container is also typicallypositioned between the two lithium elements. The subassembly is thenplaced within two mold sections and is pressed together with a suitableforce. The current collector and the insulator portion are sealedbetween the two lithium elements with a portion of the current collector(i.e., the lead) extending from the pressed together lithium elementsfor electrical connection of the electrochemical cell to a medicaldevice.

Conventionally, the lithium halves are roughened, e.g., brushed, toenhance cohesion between the pre-cut lithium halves. Cohesion of thelithium halves sealing the anode current collector therein is necessaryto prevent the cathode material from reaching the anode currentcollector and rendering the electrochemical cell inoperative. As such,techniques of enhancing such cohesion are needed.

In electrochemical cells, anode assemblies using lithium elements havebeen found to provide relatively small and efficient cells, particularlyin conjunction with cathode materials, such as iodine orthionylchloride. However, costs associated with using pre-cut lithiumhalves to form such anode assemblies is of concern. Lithium hascontinuously been increasing in price as have labor costs associatedwith each pre-cut element. As such, there is a need for anode assemblyconfigurations which at least hold the line on such costs.

Table 1 below lists U.S. Patents that describe electrochemical cellshaving thin plate anodes:

TABLE 1 U.S. Pat. No. Inventor(s) Issue Date 4,166,158 Mead, et al. Aug.28, 1979 4,359,818 Zayatz Nov. 23, 1982 4,398,346 Underhill, et al. Aug.l6, 1983 4,401,736 Zayatz Aug. 30, 1983 4,421,833 Zayatz Dec. 20, 19834,601,962 Zayatz July 22, 1986 4,812,376 Rudolph March 14, 19894,824,744 Kuo et al. April 25, 1989 5,209,994 Blattenberger et al. May11, 1993

All patents listed in Table 1 above and elsewhere herein are herebyincorporated by reference in their respective entirety. As those ofordinary skill in the art will appreciate readily upon reading theSummary of the Invention, Detailed Description of the Embodiments andClaims set forth below, many of the devices and methods disclosed in thepatents of Table 1 may be modified advantageously by using the teachingsof the present invention.

SUMMARY OF THE INVENTION

The present invention has certain objects. That is, various embodimentsof the present invention provide solutions to one or more problemsexisting in the prior art with respect to lithium elements and anodeassemblies in electrochemical cells. One such problem is obtainingsatisfactory cohesion between lithium elements in an anode assembly. Toenhance cohesion, it has been typical practice to roughen the facingsurfaces of the lithium plates by “brushing,” such as with an abrasivematerial before the plates are pressed together. Brushing leaves fresh,unoxidized lithium material exposed which coheres relatively well.However, this brushing step adds labor and time to the cost ofmanufacturing the resulting cell.

A further problem with the present two lithium element anode assembliesis that the stamping of two separate lithium elements requires arelatively significant amount of lithium material, time and labor, andgenerates excessive waste material. An arrangement that reduces scrapresulting from lithium element production, without impairing theperformance of the cell, would offer significant advantage.

Various embodiments of the present invention have the object of solvingat least one of the foregoing problems. Further, an embodiment thatrequires only a single lithium element, thereby eliminatingmanufacturing time and labor, would reduce the cost of manufacturing acell. In addition, an embodiment that minimizes the amount of scrap inproduction of the lithium elements is also advantageous. Still further,an embodiment that does not require brushing prior to pressing wouldreduce the time and cost of manufacturing.

In comparison to known lithium elements and anode assemblies, variousembodiments of the present invention may provide one or more of thefollowing advantages: eliminating one of the two separate lithiumelements, thereby reducing the time and labor required to produce thesecond lithium element; enhancing the flow of the lithium materialduring pressing which enhances the cohesion for adequate sealing of theanode current collector, thereby reducing the need for “brushing” thefacing surfaces of the lithium plates prior to pressing the platestogether; and minimizing the amount of scrap material in the productionof the lithium elements, thereby reducing the cost of the element andthus cost of the cell.

Some embodiments of the invention include one or more of the followingfeatures: a folded lithium element; a folded lithium element havingfirst and second sections in which at least a portion of the firstsection lies adjacent to at least a portion of the second section toreceive a current collector therebetween; a folded lithium elementhaving first and second sections where surface areas of the sections aresubstantially equivalent; and a folded lithium element having first andsecond sections where a surface area of the first section is less than asurface area of the second section.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an implantable medical deviceimplanted inside a human body powered by an electrochemical cell.

FIG. 2a is a cross-sectional view of an electrochemical cellincorporating an anode assembly according to the present invention.

FIG. 2b is an end cross-section view of the cell of FIG. 2a.

FIG. 3a is a plan view of an assembly of a portion of the cellillustrated in FIG. 2a, with parts shown in cross-section.

FIG. 3b is a cross-sectional view of the anode assembly shown in FIG.3a, taken along line 3 b—3 b.

FIG. 4 is a plan view of the assembly of FIG. 3a in a die, with portionsshown in cross-section.

FIG. 5a is a plan view of a preferred embodiment of a lithium elementaccording to the present invention.

FIG. 5b is a modified plan view of a partially folded lithium elementformed by the lithium element illustrated in FIG. 5a.

FIGS. 6a-6 c are plan views of alternative embodiments of a lithiumelement according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Throughout the several figures and this description, like referencenumerals designate like elements.

Electrochemical cells 1, or batteries, generate electrical current fromchemical energy. Such cells have found wide-spread use as power sourcesin medical devices 2 such as heart pacemakers implanted in a human body3, as illustrated in FIG. 1.

FIGS. 2a and 2 b show an illustrative electrochemical cell 5 includingan anode assembly 13. The cell 5 has a container or casing 10 made ofmetal, such as stainless steel, or other suitable electricallyconductive material. Container 10 has an open top or end 11 which isclosed by a lid 12, also of metal such as stainless steel. The lid 12 isattached to container 10, such as, for example, by welding.

The anode assembly 13 includes a folded lithium element 14 having anembedded anode current collector 18. The structure of the folded lithiumelement 14 and the manner in which current collector 18 is embeddedtherein will be described further below with reference to FIGS. 3-6.Current collector 18 may be an extension of an electrical lead 22extending outward of the container 10. Both the lead 22 and currentcollector 18 may be a thin conductive pin made of, for example, Alloy52, nickel, or stainless steel. Electrical lead 22 is of sufficientlength to extend out of container 10 for making an external electricalconnection thereto. Current collector 18 and lead 22 are sealed from theremainder of the cell contents by an insulator element generallydesignated 24 which surrounds lead 22 and which may take one of anynumber of configurations as known to one skilled in the art. Generally,insulator 24 is of a material which in addition to being non-conductiveis also non-reactive with the contents of the cell 5 and may be formedof, for example, fluoropolymers, ceramic, glass, plastic, etc., as isknown in the art. Many other non-reactive materials may be used forinsulator 24.

As shown in the illustrative cell 5 of FIGS. 2a and 2 b, the anodeassembly 13, which includes folded lithium element 14 and currentcollector 18, is electrically insulated from lid 12 by an insulator band30. Band 30 extends along a portion of the peripheral edge of thelithium element 14 and is also of a non-conductive, non-reactivematerial. It should be readily apparent to one skilled in the art thatcell 5 is only one illustrative embodiment of a cell incorporating afolded lithium element in accordance with the present invention. Thepresent invention is in no manner limited to such a cell configuration,but is limited only as described in the accompanying claims.

The anode assembly 13 is provided with a coating or film 20 of polymericorganic donor material, such as, for example, poly (2-vinylpyridine).The polymeric donor film 20 may take the form of a perforated film,covering the operative or opposed lateral (i.e., outer) surfaces 31, 32of anode assembly 13. As taught in U.S. Pat. No. 5,209,994, thethickness of the polymeric organic donor material can be controlled toachieve desired end-of-life voltage drop characteristics.

The anode assembly 13 is positioned in container 10 with the opposedlateral surfaces 31, 32 of the folded lithium element 14 spaced from theinner surface 35 of the container 10. Plastic clips (not shown) may beused for this positioning if desired. The anode assembly 13 ispositioned in container 10 as part of a lid and anode assembly, such asassembly 50, shown in FIG. 3a and further described below.

The lid and anode assembly includes anode assembly 13 and a lid 12 whichcan be welded to container 10. Further, the assembly 50 includes afeedthrough ferrule 33 and a fillport 34 extending from lid 12 into theinterior of the container 10. Electrical lead 22 extends through thefeedthrough 33 to the exterior of the cell. It should be readilyapparent that any lid, feedthrough, fillport, insulative structure iscontemplated for use in accordance with the present invention. Thepresent invention is in no manner limited to any particularconfigurations or materials for such elements.

Container 10 defines an interior cell cavity 37 which is filled withcathode material 36, such as halogen cathode materials, for example,iodine containing cathode materials or thionylchloride. The cathodematerial 36 operatively contacts the exposed (i.e., operative) surfaces31, 32 of the folded lithium element 14. The amount of cathode material36 in the container is preferably sufficient to contact the exposedlateral surfaces 31, 32 of folded lithium element 14 and to reach alevel at or adjacent the interior surface of lid 12. The opening, i.e.,fillport, in lid if is hermetically sealed, for example, with a seriesof closure members or plugs.

In operation, container 10, being of electrically conductive material,serves as a cathode current collector in direct contact with the cathodematerial 36 in container 10. Consequently, an electrical lead (notshown) may be attached directly to the exterior of container 10 forcathodic contact. Another electrical lead can be connected to theelectrical lead 22 to make electrical connection with the anode assembly13. A chemical reaction between the lithium element 14 and the cathodematerial 36 in container 10 causes electrons to flow into the currentcollector 18. A chemical reaction between the cathode material 36 andthe container 10 causes the container 10 to be positively charged. Theresulting voltage differential across the cell 5 is used to generatepower for a medical device.

To prevent the cell 5 from short-circuiting, the current collector 18 isisolated from the cathodic container 10 and from the cathode material 36which fills container 10. As noted above, an insulator 24 allows thecurrent collector 18 to extend to the exterior of the container 10without making electrical contact with the cathodic container 10.Additionally, the current collector 18 is protected from contact withthe cathode material 36 by the seal formed by the folded lithium element14 about the current conductor 18 embedded therein.

FIG. 3a shows one embodiment of an anode and lid assembly 50 that formspart of the cell 5. Assembly 50 includes the anode assembly 13, the lid12 including fillport 34 and ferrule 33, insulator 24 and insulator band30. As noted above, the anode assembly 13 includes folded lithiumelement 14 and current collector 18 embedded therein. In the embodimentillustrated in FIGS. 3a and 3 b, folded lithium element 14 is formed byfolding one section 141 of lithium element 14 along a fold line 120 suchthat a portion 125 of another section 140 of the lithium element 14 liesadjacent portion 126 of section 141. Portion 125 is not visible in FIG.3a because it is covered by portion 126, but is illustrated in FIGS. 3band 5. Current collector 18 is interposed or sandwiched between theportions 125, 126 of folded lithium element 14. A part 135 of insulator24 is also sandwiched between portions 125 and 126. Insulator band 30extends along a portion of peripheral edge 137 of folded lithium element14 forming a barrier between the lithium element 14 and the lid 12 topreclude electrical contact therebetween.

Generally, the lithium element 14 includes two sections 140 and 141divided by fold line 120. Sections 140 and 141 are foldable hinged toeach other. Fold line 120 is defined herein as only referring to theposition at which the sections of the foldable lithium element areconnected. The fold line 120 need not have any structural differencesthan the remainder of the lithium element 14. In other words, the foldline is not perforated, pre creased, or structurally altered in anymanner prior to folding. However, such structural alteration or liketechniques may be used.

In the embodiment shown in FIG. 3a, section 141 is smaller in surfacearea than section 140 such that section 141 covers only a portion ofsection 140. That is, the portion 126 of section 140 is smaller than thesurface area of section 140. However, as described below, various otherconfigurations are contemplated according to the present invention. Thesurface area of smaller section 141 need only be large enough tocompletely cover the current collector 18 and a portion 135 of insulator24, so that after pressing the current collector 18 is sealed fromexposure to the contents of the cell, particularly the cathode material.

FIG. 3b shows a cross-sectional view of the lid and anode assembly 50taken at line 3 b—3 b. The cross-sectional view shows the donor material20 coating the outer surfaces of the folded lithium element 14. Thecurrent collector 18 lies substantially centered between the twothicknesses of sections 140, 141.

FIG. 4 shows assembly 50 in a die 150 that is used to press the foldedlithium element 14. The die 150 defines a cavity 160 that is sized andshaped to receive assembly 50 and to exert pressure on the lithiumelement 14 when a portion of the die is closed over the assembly 50.Further, the cavity 160 is sized to leave a small gap 165 between theperiphery of lithium element 14 and the wall defining the cavity 160.

It has been found that the cohesion achieved between the portions 125and 126 of the lithium element 14 illustrated in FIGS. 3, 4 and 5, isparticularly good due to the manner in which the lithium material oflithium element 14 responds when pressed. More specifically, it has beenfound that, when pressed, the lithium material of portion 126 is able toflow into the areas of section 140 that are not covered by the initialunpressed section 141. That is, the material from the double-thicknessarea flows into the area that is only a single thickness, particularlyinto the single thickness area surrounding the portion 126. Thisdisplacement, disruption, or relocation of the lithium material exposesfresh lithium metal without any oxides. The unoxidized lithium materialyields better cohesion between the pressed portions 125, 126 than isachieved in prior art arrangements wherein two lithium plates ofgenerally the same size and shape are pressed together.

With the prior art two-element arrangement, rough-hewing of the facingsurfaces of the lithium elements such as with an abrasive material priorto pressing is typically performed. Using differently sized sections,such that a relatively large displacement of material of at least onewith respect to the other is achieved, reduces and potentiallyeliminates the need for rough-hewing of the facing surfaces prior topressing.

As described further below with respect to embodiments which includesections that have substantially equivalent surface areas, by maximizingthe gap 165 size, the need for surface rough-hewing may also be reduced.The size of gap 165 may be defined as being oversized relative to theunpressed anode assembly. Such over sizing may be in the range of about0.010 inch (0.0254 cm) to about 0.050 inch (0.127 cm), preferably about0.010 inch (0.0254 cm) to about 0.020 inch (0.0508 cm). However, due tolimitations in the pressing of the anode assembly, particularly crackingof the donor material covering the lithium sections, the amount ofdisplacement accomplished using gap 165 and, thus, the gap size, islimited. In other words, too large of a gap 165, which allows increasedlithium displacement for better cohesion between the sections, may leadto cracking of the donor material covering the lithium element.

FIGS. 5a-5 b and 6 a-6 c show various embodiments of a foldable lithiumblank (i.e., pre-cut 200, 300, 400, 500) in planar or unfolded form, asit would be provided after manufacture. Such pre-cuts may be provided,such as by stamping from a sheet of lithium material. For convenientreference, the embodiment illustrated in FIG. 5 will be identified as a“flap pre-cut” and the alternative embodiments illustrated in FIGS. 6a,6 b, and 6 c will be identified as “mirror-image pre-cuts.” Any of thesepre-cuts, when folded, can form folded lithium element 14 and can beused for an anode assembly 13.

The flap pre-cut 200 of FIGS. 5a and 5 b has first and second opposedlateral surfaces 201, 202, and terminates at peripheral edge 203. Flappre-cut 200 includes a main body section 204 which is completelyintegral with a flap section 205. Completely integral as used hereinmeans being of a single continuous body of material. Dotted line 210indicates a shared edge of flap section 205 and main body section 204.Line 210 further represents where the pre-cut 200 will be folded in use.

Main body section 204 terminates in a peripheral edge 215 whichgenerally defines a shape approximately the same, but slightly smallerthan the cell cavity into which the folded lithium element 14 made fromthe pre-cut 200 will be placed. Generally, the size and shape of thelithium element 14 is to be maximized, for maximum surface area contactwith the cathode material, within the constraints of the size and shapeof the cell cavity in which it is placed.

Flap section 205 terminates in a peripheral edge 220 that, in theembodiment illustrated in FIG. 5, generally defines a rectangle havingsurface area that is less than the surface area of main body section204. When folded, flap section 205 lies adjacent portion 225 of mainbody section 204. The portion 226 of flap section 204 is substantiallythe whole of flap section 205. The portion 225 of main body section 204is delineated by dotted lines 230, 231, 232, and 210, and has a size andshape substantially the same as that of the portion 226 of flap section205. Thus, the portion 225 of main body section 204 has a surface areathat is less than the entire surface area of the main body section 204and the flap section 205 (and, thus, portion 226 of flap portion 205)has a surface area that is less than the surface area of the main bodysection of 204.

It will be understood by those of skill in the art that the peripheralshapes and sizes of main body section 204 and flap section 205 can bevaried substantially within the scope of this invention, as defined inthe accompanying claims. For example, flap section 205 could besemi-circular, elliptical, or any other suitable shape. It is onlynecessary that the flap section 205 be sized and shaped such that itwill be able to cover the current collector 18 that will be sandwichedbetween the portions 225, 226 of flap section 205 and main body section204. The shape and size of main body section 204 can be varied toaccommodate a cell cavity 37 of other shapes and sizes. Further, itshould be apparent that the current collector 18 may be positionedwithin an anode assembly in various locations. For example, the currentcollector need not be located in a parallel manner to the lid, but canextend at an angle or perpendicular to the lid. Therefore, the shape andsize of flap section 205 may additionally take various otherconfigurations corresponding to the locations of the current collector,so long as the flap section 205 when folded over main body section 204covers the collector 18.

FIGS. 6a-6 c show additional embodiments of a foldable lithium elementaccording to the present invention. These three embodiments share thecharacteristic that they each include two integrally connected sectionsthat are mirror-images of one another about a line that is used as afold line to form a folded lithium element 14. A myriad of pre-cutshapes could be generated that would share this characteristic and areconsidered to be within the scope of this invention.

The mirror-image pre-cut 300 shown in FIG. 6a has first and secondopposed lateral surfaces 301, 302 which terminate at peripheral edge303. Pre-cut 300 includes a main body section 304 that is completelyintegral with a mirror-image section 305. Dotted line 310 indicates anedge shared by main body section 304 and mirror-image section 305. Line310 further represents where the pre-cut 300 will be folded in use. Mainbody section 304 terminates in a peripheral edge 315 which generallydefines a shape approximately the same but slightly smaller than thecell cavity 37 into which the folded lithium element 14 will be placed.As previously described, it is typical practice for the size and shapeof the lithium element to be maximized. Mirror-image section 305terminates in a peripheral edge 320.

When folded, main body section 304 and mirror-image section 305 havesurfaces lying adjacent to one another. As the sections 304 and 305 aremirror images, the peripheral edges 315 and 320 are generally aligned ormatched with each other. Thus, the portions of sections 304 and 305lying adjacent to one another are substantially the whole of sections304 and 305, respectively.

The mirror-image pre-cut 400 shown in FIG. 6b has first and secondopposed lateral surfaces 401, 402 which terminate at peripheral edge403. Pre-cut 400 includes a main body section 404 that is completelyintegral with a mirror-image section 405. Dotted line 410 indicates anedge shared by main body section 404 and mirror-image section 405. Line410 further represents where the pre-cut 400 will be folded in use. Mainbody section 404 terminates in a peripheral edge 415 which generallydefines a shape approximately the same but slightly smaller than thecell cavity 37 into which the folded lithium element 14 will be placed.Mirror-image section 405 terminates in a peripheral edge 420.

When folded, main body section 404 and mirror-image section 405 havesurfaces lying adjacent to one another. As the sections 404, 405 aremirror images, peripheral edges 415 and 420 are generally aligned ormatched with each other. Thus, the portions of sections 404 and 405lying adjacent to one another are substantially the whole of sections404 and 405, respectively.

The mirror-image pre-cut 500 shown in FIG. 6c has first and secondopposed lateral surfaces 501, 502 which terminate at peripheral edge503. Pre-cut 500 includes a main body section 504 that is completelyintegral with a mirror-image section 505. Dotted line 510 indicates anedge shared by main body section 504 and mirror-image section 505. Line510 further represents where the pre-cut 500 will be folded in use. Mainbody section 504 terminates in a peripheral edge 515 which generallydefines a shape approximately the same but slightly smaller than thecell cavity 37 into which the folded lithium element 14 will be placed.Mirror-image section 505 terminates in a peripheral edge 520.

When folded, main body section 504 and mirror-image section 505 havesurfaces lying adjacent to one another. As the sections 504, 505 aremirror images, peripheral edges 515 and 520 are generally aligned ormatched with each other. Thus, the portions of sections 504 and 505lying adjacent to one another when the pre-cut is folded aresubstantially the whole of sections 504 and 505, respectively.

It will be understood by those of skill in the art that the peripheralshapes of main body sections 304, 404, 504 and mirror image sections305, 405, 505 can be varied substantially within the spirit of thisinvention. For example, the line about which the main body section ismirrored can be anywhere along the peripheral edge of main body section304, 404, 504. Further, the shape of main body section 304, 404, 504 andits mirror-image can be altered to accommodate cell cavities of variousother shapes.

Typically, the thickness of the flap pre-cut used is in the range ofabout 0.060 inch (0.152 cm) to about 0.080 inch (0.203 cm), preferablyabout 0.072 inch (0.183 cm) to about 0.078 inch (0.198 cm). Typically,the thickness of the mirror-image pre-cuts is in the range of about0.038 inch (0.097 cm) to about 0.048 inch (0.122 cm), preferably about0.042 inch (0.107 cm) to about 0.044 inch (0.112 cm).

The present invention is further directed to methods of making orforming anode assemblies for electrochemical cells. Generally, a lithiumpre-cut, as described herein, is folded such that at least a portion ofa first section of the pre-cut lies adjacent at least a portion of asecond section of the pre-cut. A current collector is placed between theportions of the pre-cut such that it is in contact therewith. Thecurrent collector encompassed in the folded pre-cut is then positionedin a die and pressed with sufficient force to achieve cohesion betweenadjacent portions of the sections.

Preferably, as shown in FIG. 4, a lid and anode assembly 50 includingthe anode assembly 13 and the cell lid 12 is constructed prior topressing the folded lithium element 14. More specifically, the anodeassembly 13 is attached to the lid 12 of a cell 5 with an insulator band30 positioned between the lithium element 14 and the lid 12. Electricallead 22 extends through the feedthrough ferrule 33 in the lid 12. Thisanode and lid assembly 50 is then placed in a die 150 and the lithiumelement 14 is pressed with sufficient force to achieve cohesion betweenportions 125 and 126 of the sections 140 and 141. The force used toperform such pressing will vary depending on the amount of material tobe displaced, the shape and size of the lithium element, and variousother factors. Typically, the pressure applied is in the range of about1100 psi (75 atmospheres) to about 5900 psi (401 atmospheres),preferably about 2300 psi (156 atmospheres) to about 3500 psi (238atmospheres).

After pressing, the assembly 50 is then inserted into the container 10,and the lid 12 is welded to the container 10. Cathode material 36 ispoured into the cell cavity 37 through a fillport 34 in the lid 12. Thefillport 34 is sealed with suitable plugs, such as stainless steel forthe portion of the fillport 34 adjacent the lid 12 and such as Teflonfor the portion of the fillport 34 that is in contact with the insulatorband 30. The feedthrough ferrule 33 is sealed with a non-conductivematerial, such as glass.

When this method is employed with a mirror-image pre-cut 300, 400, 500,such as those illustrated in FIGS. 6a, 6 b, and 6 c, a layer or film ofdonor material can be positioned adjacent to each of the lateralopposing surfaces 301 and 302, 401 and 402, 501 and 502 of lithiumelement when the anode assembly is positioned in the die 150, such thatthe donor material film 20 is applied during pressing of the lithiumelement. Further, as the sections of the pre-cut are mirror images,displacement of material for enhancement of cohesion of the adjacentsurfaces of the sections occurs primarily at the periphery of the foldedlithium element as the material displaces into gap 165.

When the flap section 141 is pressed with the main body section 140,displacement of the lithium material of the flap section 141 over alarger area of the main body section 140 occurs. This displacementreduces the need for and possibly eliminates the need for rough-hewingthe adjacent surfaces prior to pressing. Further, displacement oflithium into gap 165 occurs creating even better cohesion at theperiphery of the folded lithium element.

When this method is employed with a flap pre-cut 200, such as thatillustrated in FIG. 5a, it has been found that the donor material filmis applied in two process steps. First, a film of donor material isapplied adjacent the main body section 204 before lithium element 14 hasbeen pressed. After pressing and displacement of the lithium material ofthe flap section during pressing, a donor material film is applied overthe other surface and thereafter once again pressed.

The preceding specific embodiments are illustrative of the practice ofthe invention. It is to be understood, therefore, that other expedientsknown to those skilled in the art or disclosed herein may be employedwithout departing from the invention or the scope of the appendedclaims. For example, the present invention is not limited to lithiumelements having the particular peripheral shapes of the examplesillustrated in FIGS. 5 and 6a-6 c. The present invention furtherincludes within its scope other methods of making and using theinvention described herein above.

What is claimed is:
 1. An anode assembly for an electrochemical cell,the assembly comprising: a current collector element; a folded sheetlithium element having the current collector element embedded thereinbetween first and second opposing sections of the folded sheet lithiumelement defined on opposite sides of a single fold line; said foldedsheet lithium element having a first surface of the first section and afirst surface of the second section pressed against the currentcollector element; and an insulator barrier band extending along aportion of the peripheral edge of the folded sheet lithium element. 2.The anode assembly according to claim 1, wherein the first section ispre-cut with a first shape and a first area and the second section ispre-cut with a second shape that is substantially the mirror image ofthe first shape in reference to the fold line and a second area that issubstantially the same as the first area and encloses said currentcollector between said first surface of said first section and saidfirst surface of said second section.
 3. The assembly according to claim1, wherein the first section has a first shape and a first area, thesecond section has a second shape that differs from the first shape anda second area that exceeds said first area, and said first surface ofsaid first section is folded against at least a portion of said firstsurface of said second section and encloses said current collectorbetween said first surface of said first section and said first surfaceof said second section.
 4. The assembly according to claim 1, whereinthe first section has a first shape and a first area, the second sectionhas a second shape that differs from the first shape and a second areathat exceeds said first area, and said first surface of said firstsection is folded against at least a portion of said first surface ofsaid second section and encloses said current collector between saidfirst surface of said first section and said first surface of saidsecond section.
 5. The anode assembly according to claim 1, wherein thefirst section has a tab shape and a tab area and the second section hasa second shape that is correlated to the shape of a cell container thatthe anode is to be fitted into and that differs from the tab shape and asecond area that exceeds said first area, and said first surface of saidfirst section is folded against at least a portion of said first surfaceof said second section and encloses said current collector between saidfirst surface of said first section and said first surface of saidsecond section.